Separable Reversible Data hiding in Encrypted Images by n-nary Histogram Modification

This work proposes a novel scheme of separable reversible data hiding for encrypted image using histogram modification. After the original image is encrypted by the sender, the data-hider embeds the secret message into the encrypted image by a histogram modification and n-nary data hiding scheme. On the receiver side, the secret message can be extracted by the embedding key, and the original image can be totally recovered using both the embedding key and the encryption key. If the embedding key is unavailable for the receiver, the original image can still be approximately recovered using the encryption-key. This separable method does not require the sender to reserve embedding room by himself, and can perfectly recover the original image. Compared to the existing reversible data hiding methods for encrypted images, the proposed method largely improves the embedding capacity.